White-label: title/logo now driven by conf (closes #6)

conf.name was already plumbed into routes/index.js's values object,
but never actually rendered anywhere -- <title>, the navbar brand,
and the favicon were all still hardcoded "SSO - Theta 42"/"SSO
Manager". Now render <%- name %>/<%- logo %> in top.ejs; new
conf.logo key (default: the existing theta42.svg) drives the navbar
image and favicon.

Also fixes a pre-existing broken favicon: top.ejs referenced
/static/favicon.svg, which was never actually served from public/ --
only public/img/theta42.svg existed. The favicon now uses that same
file via conf.logo instead of a nonexistent path.

Footer copyright/logo/GitHub links are left as-is (open-source
attribution, not deployment branding).

nodejs/routes/index.js

@@ -14,6 +14,7 @@ const values ={
   title: conf.environment !== 'production' ? `dev` : '',
   titleIcon: conf.environment !== 'production' ? `<i class="fa-brands fa-dev"></i>` : '',
   name: conf.name,
+  logo: conf.logo,
   ...buildInfo,
 }